There is a growing awareness of the lack of satisfactory products designed for mobile persons with incontinent infirmities. While sanitary napkins, pantiliners, disposable briefs and diapers are available for the mobile incontinent person, such products are not satisfactory from either a comfort or a protection standpoint. Catamenial products such as pantiliners and sanitary napkins are very comfortable to use. However, these products fail to achieve a satisfactory level of containment for high void levels of urine. While diapers and briefs meet the containment needs of the incontinent person, these products lack the comfort and discreteness available from sanitary napkins and pantiliners.
Thus, it is desirable to provide an absorbent article such as an incontinent pad that is comfortable and discrete, yet provides superior protection and containment. In order to achieve the goal of providing such an absorbent article, it is necessary that the absorbent article be capable of rapidly accepting and containing a large volume of liquid within a small surface area; rapidly distributing the liquid efficiently throughout the product; conforming to the body of the wearer; maintaining good body contact (i.e., the maintenance of the article in close proximity to and in conformity with the body of the wearer); and maintaining its integrity even when wetted so as to be effective to accept and contain a subsequent discharge or gush of liquid and to prevent rewet (i.e., recontact of liquids contained in the article with the skin of the wearer due to forces that squeeze the liquid out of the article).
One of the methods for enhancing the absorptivity of such products is to provide a void space or reservoir that is located near the top surface of the article. Examples of these type of products are disclosed in U.S. Pat. No. 3,364,931 issued Jan. 23, 1968 to W. F. Hirsch; U.S. Pat. No. 4,029,101 issued June 14, 1977 to Chesky et al., and U.S. Pat. No. 4,501,586 issued Feb. 26, 1985 to Holtman. Such articles, while providing some measure of increased ability to accept large volumes of liquid, are often incapable of both effectively accepting a subsequent discharge or gush of liquid and preventing rewet. This is due to the lack of integrity or form retention capacity of the materials after being wetted. Absorbent cores such as those formed of creped wadding or cellulosic fibers have a tendency to split, ball or lump when wetted. They thereby become relatively shapeless and non-form-sustaining. These elements also tend to flatten out and become compacted when subjected to forces. Because an absorbent article is subject to various forces during use, the article will tend to lose its shape when wetted. Thus, it will not conform to the body of the wearer resulting in discomfort for the wearer. In addition, the wetted and compressed absorbent core will have lost its ability to absorb a subsequent discharge or gush of liquid resulting in an increased likelihood of leakage and failure of the product. Further, because the void space or reservoir tends to lose its size and shape, not only is there a decreased ability to contain high volumes, but there is also an increased danger of rewet as the overwrap is no longer spaced away from the absorbent core.
Thus, there is a need to provide an absorbent article wherein the article will retain its shape after being wetted so as both to remain comfortable and to be able to rapidly absorb and contain a subsequent gush of liquid without increasing the likelihood of leakage or rewet. Accordingly, it would be advantageous to provide an absorbent article that is moisture insensitive without a loss in comfort or absorbent capacity. It would also be advantageous to provide an article having increased absorption and increased comfort.
Another method for increasing the absorbency of absorbent articles is to provide them with water-insoluble hydrogels. Water-insoluble hydrogels are polymeric materials which are capable to absorbing large quantities of liquids and which are further capable of retaining such absorbed liquids under moderate pressures. These absorption characteristics of water-insoluble hydrogels make such materials especially useful for incorporation into absorbent articles such as incontinent pads.
The effectiveness of liquid-absorbing hydrogel materials in disposable absorbent articles can be quite dependent upon the form, position and/or manner in which the hydrogel material is incorporated into the absorbent article. In some cases, for example, the effectiveness of hydrogel liquid absorption in absorbent articles can be adversely affected by a phenomenon called "gel blocking". The term gel blocking describes a situation that occurs when a hydrogel particle, film, fiber, composite, etc. is wetted. Upon wetting, the surface of the hydrogel material swells and inhibits liquid transmission to the interior of the absorbent material. Wetting of the interior subsequently takes place via a very slow diffusion process. In practical terms, this means that absorption of liquid by the article is much slower than discharge of liquid to be absorbed, and failure of the absorbent article may take place well before the hydrogel material in the absorbent article is fully saturated.
Thus, there is a continuing need to identify hydrogel-containing absorbent articles wherein the hydrogel material is especially effective and efficient in performing its intended function of holding discharged body liquid without interfering with the acquisition and distribution of body liquids by and within the article. Hydrogel materials are generally significantly more expensive than readily available absorbent fiber materials (e.g. cellulose fibers). Accordingly it would be advantageous to provide articles wherein either absorbent capacity of the hydrogel-containing article can be improved or wherein a given absorbent capacity of an article can be maintained while reducing the amount of relatively expensive hydrogel material used. It would also be advantageous to provide articles wherein the liquid-storing hydrogel material does not adversely affect the ability of the absorbent article to quickly acquire discharged body liquids.
In addition, because hydrogel material swells and expands upon being wetted, the hydrogel-containing absorbent core also must expand. Because the overwrap is generally firmly affixed around the absorbent article, the only space available for expansion of the absorbent core is within the interior of the absorbent article. This is especially important for incontinent pads or other absorbent articles that have a void space or reservoir within the article. The hydrogel-containing absorbent core will thus expand into the void spaces resulting in a loss of void space, i.e., acquisition area. In addition, if there is no void space within which the absorbent core can expand, the core will be squeezed and compressed resulting in an increased danger of rewet. Therefore, there is a need to identify hydrogel-containing absorbent articles wherein the overwrap can expand as the hydrogel expands. Accordingly, it would be advantageous to provide articles wherein an expansion means allows the overwrap to continually adjust as the hydrogel expands. It would also be advantageous to provide articles wherein the manufactured size of the void spaces and channels are maintained during expansion of the article.
Therefore, it is an object of the present invention to provide an absorbent article which is able to rapidly accept and contain a large void of body liquids without leakage.
It is an additional object of the present invention to provide an absorbent article having improved comfort in both the wet and dry state for the wearer.
It is a further object of the present invention to provide an absorbent article having a resilient shaping member which is moisture insensitive so as to provide an acquisition channel to quickly accept and contain large voids of body liquid, and to prevent these liquids from passing back through the topsheet to rewet the wearer.
It is also an object of the present invention to provide an absorbent article having a liquid impervious shelf to move efficiently utilize the hydrogel material capacity of the absorbent core.
It is a further object of the present invention to provide an absorbent article having an overwrap and a releasing means so that when the hydrogel-containing absorbent core expands when wetted, the overwrap will expand maintaining the surface area of the article and at least maintaining and possibly increasing the volume of the liquid acquisition zone during use.
These and other objects of the invention will be more readily apparent when considered and referenced to the following description and when taken in conjunction with the accompanying drawings.